1. Field of the Invention
This invention relates to a coupling device having a hook for connection with belts, ropes, chains or the like used in lifting or otherwise handling cargoes and other objects.
2. Prior Art
Numerous coupling devices of the above-mentioned character have been proposed, a typical example of which is disclosed in Japanese Utility Model Publication No. 2-10329. This prior device shown in FIG. 13 of the accompanying drawings generally comprises a shaft member 100 carrying on its upper end a coupling ring 101 via a rotary member 102, a cylindrical sleeve 103 vertically movable relative to the shaft 100, a hook 104 disposed at the lower end of the sleeve 103 for anchoring a rope 105 or the like, a coil spring 106 normally biasing the sleeve 103 downwardly, and a stopper member 107 connected to the rotary member 102 and shiftable between the solid line and phantom line positions for releasably holding the sleeve 103 in its lowermost position in which the hook 104 is closed. Such a prior art device has a drawback in that it is made up of so many component parts that their assembly is complicated and time-consuming. It involves mounting the rotary member 102 on the shaft member 100, connecting the rotary member 102 with the coupling ring 101 and the stopper member 107, and putting the hook 104 into threaded engagement with the shaft 100. Another drawback is that since the coil spring 105 and the hook 104 are supported on a support rib 108 formed internally of the sleeve 103 at a position above and remote from a lower end 109 of the sleeve 103 which extends across the U-shaped portion of the hook 104, there is a fear that the rope 105 will push up the lower end 109 of the sleeve 103 and disengage from the hook 104 in the event that the stopper member 107 fails to properly function under the influence of external pressure or shock.